Last updated on May 12, 2019 at 12:32
Ischaemic heart disease
This topic is very similar to the corresponding pathophysiology topic.
Since cardiomyocytes generate almost all their energy from oxidative phosphorylation are they strictly dependent on continuous flow of oxygenated blood. Ischaemic heart disease is an umbrella term that includes several diseases caused by myocardial ischaemia, where there is an imbalance between coronary perfusion and the myocardium’s oxygen and nutritional requirements.
In more than 90% of cases does the ischaemia occur due to obstructive atherosclerotic plaques in the coronaries, a condition called coronary artery disease. These terms are therefore often used interchangeably, but they’re actually two different things. The remaining 10% occurs due to:
- Abnormally increased demand
- Diminished blood volume
- Diminished oxygenation of blood
- Diminished oxygen-carrying capacity of blood
Symptoms usually occur when the atherosclerotic plaque occludes more than 70% of the lumen. At this point has the critical stenosis point been reached.
Four diseases fall under the “ischaemic heart disease” umbrella term. They are:
- Myocardial infarct
- Angina pectoris
- Chronic ischaemic heart disease
- Sudden cardiac death
Strictly speaking is angina pectoris just the name of the characteristic pain associated with different types of ischaemic heart disease. Three important forms exist:
- Stable angina is the most common form. A critical stenosis is present, but the perfusion of the myocardium is still sufficient in rest. However, as soon as the myocardial blood requirement increases, such as during walking up stairs or exercise, will the perfusion be insufficient for the myocardium. This causes the angina pectoris pain. Symptoms are relieved upon rest or after application of nitro-glycerine, a vasodilator.
- Prinzmetal’s angina isn’t associated with coronary artery disease at all, although it can also be present. In Prinzmetal’s angina is there a strong vasospasm of an epicardial artery, which decreases the perfusion. This type of angina is unrelated to physical activity, heart rate or blood pressure.
- Unstable angina is the condition where angina pectoris can occur even in rest. Morphologically it happens because of a thrombosis stuck to a plaque, which is kinda loose so it sometimes blocks the artery and sometimes not. Unstable angina is usually a warning sign that an acute myocardial infarct may occur in the near future.
Chronic ischaemic heart disease
Chronic IHD (or ischaemic cardiomyopathy) is a progressive heart failure that occurs due to ischaemic myocardial damage. The myocardial damage is often due to a previous myocardial infarct, but in some cases can severe coronary artery disease cause myocardial ischaemia and dysfunction without infarction or symptoms.
The healthy myocardium that isn’t damaged by ischaemia will always try to compensate for the damaged myocardium. Left ventricular hypertrophy and dilation are usual findings, along with fibrosis of the damaged myocardium. Microscopically we find myocardial hypertrophy, fibrosis and diffuse subendocardial vacuolization.
Sudden cardiac death
Sudden cardiac death is defined as unexpected death from cardiac causes early after the onset of symptoms, or without symptoms. It’s often the first clinical manifestation of ischaemic heart disease, meaning that it occurs without warning. Other non-ischaemic causes include:
- Congenital heart disease
- Aortic valve stenosis
- Mitral prolapse
- Dilated cardiomyopathy
- Hypertrophic cardiomyopathy
- Pulmonary hypertension
- Hypertensive hypertrophy
- Abnormalities of the electrical conduction system
No matter the cause, what actually kills you in the end is a lethal arrhythmia, either asystole or ventricular fibrillation.
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